Introduction: Make a Folding Locking Pocket Knife From a MTB Disk Brake

About: Second year engineering student studying at the Beautiful Okanagan campus of The University of British Columbia. I like to tinker with electronics and meddeling with 3D printing. I also have a penchant for rea…

First off I consider knives to be tools NOT weapons. Please use them responsibly, every time someone uses a knife as a weapon it makes it more difficult/Illegal to carry these very useful and potentialy life saving devices. (that is a bit of an extreme example)

Next a little about this project: It is a small knife (2in handle, 1.5in blade), however it can be scaled up. It also features a pocket clip that can be used as a money clip. It uses a lock of my own design (I think), and like most of my other projects, it is built out of scrap.

An equivalent product would be something like this

In terms of sharpness and toughness, it is equivalent to most "Stainless Steel" knifes.  If you don't know knifes, and S30V and 420HC are just gibberish,  then it it probably the same as the pocket knife you have (or used to have).

The opening picture shows three pocket knives that me and my brother built from an old mountain bike disk.  The smallest is the one I will be featuring in this instructable. The larger wooden one is much simpler and does not lock. The all metal one also doesn't lock (because of our sub par metal working skills) and it is also not sharp as sharpening the inside edge of a circle is difficult.

Thanks for reading.
Also this is an entry in the "I Could Make That Contest" and if you like it all votes are greatly appreciated.

p.s If you are looking for a pocketknife built out of high quality materials, that will look a bit more professional. I am currently in the process of making and testing a forge, and then ordering and making a S30V and Micarta folder. So stay tuned. In the meantime I recommend This instructable to get started.

Step 1: Materials and Tools

Things you'll need:
Disk Brake: Disk brakes work well for making knives because they have already been heat treated at the factory. And depending on how hard they were used they have already been annealed.  This saves you the trouble of building a forge. (beware it is very hard and may dull out your hacksaw and/or drill bits)
Hack Saw: Used for cutting the metal. if you have never owned one they are relatively cheap. Here is how to use it, it is NOT the same as a wood saw.
Coping Saw: Used for the creation of handle scales.
Vice: Multipurpose a shop essential.
Scrap Wood: If you have you're choice use something hard and nice looking.(Insert sexual joke here)  Mine had a habit of splitting. Best size is probably about 6in by 4in and about 1/8in thick.
Grinder: Not sure what grade of stones are on mine.
File: This is the most important piece of equipment if you don't have a grinder. It will take longer but it's cheaper and will get the job done.
Drill: Preferably electric but a hand drill will work, albeit more slowly.
Drill Bits:  The best will be Titanium Carbide but I think I just used standard ones.
Sand Paper: One rough maybe 100 or 80 and another thats fine 220 300.
One Bolt and Nut and Washer Combo: This will be used as the pivot screw for the blade.
Safety Glasses: the eyes are immeasurable more expensive then wearing some uncomfortable glasses while using the grinder.
Sharpy or Pencil: To mark the blade and scale shapes.
Thin sheet metal: If you can bend it by hand and it stays then it is good enough. I think mine was a piece of air duct or something.
Hammer and counter set:  Hammer is essential counter set not so much but it makes it easier to place holes on the disk brake.
Finishing Nails: Used to secure the handle together.  if possible long air nailer nails will work better.
Tin snips:  not essential but definitely easier to cut the sheet metal with than the hacksaw.
Sharpening Stones:  These will make a peice of metal into a knife, you want at least an auto parts store dual whetstone, however if you are interested in knifes either in the kitchen or hobby than a good set will serve you well. I used a old no name brand stone that normally sharpens axes, and then a couple of high quality made in japan hand me downs.
Dog:  again not essential, but works wonders to ease frustration and chew finished handle scales into saw dust :)

Step 2: Basic Knife Components and Shape

If you don't know allot about pocket knives here is a list of the different components that make up a knife. They key points are the flipper, pivot screw, handle scales.  So now you will know what I'm talking about. 

Next is deciding how big you want your knife to be and cutting it out of the disk brake. Larger knifes are, In my mind harder to make when they are folders.  The larger blade exerts more force on the locking mechanism and takes longer to sharpen.

It's really a moot point however as using a disk brake limits the size of knife you can make. The small one that I made is easier to sharpen than the large one and it it less curved which makes it more practical. I would say that you don't want to go larger than the large one in the title picture, and probably not much smaller than the one I am describing in this instructable. 

When cutting the knife out be aware that you want about 2cm longer that the cutting edge that you want, because it will be used as the tang and flipper.

Next mark out the shape on the disk and cut with hacksaw. Depending on how you plan to use this knife you'll want to decide between a point (like the large bannana knife) or rounded like the small "peanut knife". A point is useful for fine detail or puncturing boxes or tape, but it also looks intimidating (thanks to the people who threaten people with pocket knives). The rounded tip is less useful but less intimidating.

Next file off the burrs and smooth it a bit, so you don't cut your self while handling it.

Step 3: Designing the Handle Scales

(please be aware that my pictures for this step are not entirely accurate.)

The next step is to make the handle scales. Trace the outline of the blade onto the wood. (this is were the picture is wrong) Next take off about 0.5 cm on the flat end to save yourself some cutting and sanding later.  Also leave about 2 to 3mm around the outside so that when the blade is closed the edge is safely hidden away  and not slicing your pocket. 

When the scales are cut out, depending on the thickness of your wood you may have to either cut or sand them to the right thickness. Also you may want to make relief cuts on the curves to avoid bending/snapping your saw blade. Beware that these thin blades get really hot, hot enough to scorch the wood. So it is best to cut slowly or wait a while between fast and furious cuts.

Step 4: Pivot Point

The next piece of the knife is the pivot screw, or in my case pivot bolt. I first placed the blade on the scales and decided about were I wanted the pivot to be about 2mm down from the top of the wood., so that I would have a flipper and the blade would be completely enclosed.

Next try and pivot the blade around this point using your fingers to hold it in place. you want the edge to line up with the edge of the handle when open but to be a safe distance away when closed. This takes some trial and error, but once you have the spot, hopefully your disk brake either has a hole there or is completely solid. If not you will need to get inventive.

Then take the hammer and the center punch and place a dent were the hole should be. Also depending on the drill bits your using you will want to have water or oil on the blade to cool down and lubricate the bit.

Used a Small drill bit first and gradually work your way up in diameter until it is the same size as the bolt you are using.

Repeat the procces (minus the center punch) on the wooden scales.  A test fit will allow you to test the action of the knife.

Step 5: The Lock

The lock that I used on this knife is not traditional, but it works pretty well and is way easier to make.

It is a piece of metal  that goes through the scale and is bent 90 degrees inside the knife, it is then bent another 90 degrees on the outside of the knife. Pulling on (perpendicular to the scale) it will release the blade while pushing it will slide it across so that it blocks the movement of the knife while it is open. It's a little hard to explain hopefully the pictures will help.

Start off by cutting a piece of sheet metal about the same size as both scales laid end to end. Then trace an outline of the scales onto the metal, leave a gap between the ends that is the same length as the distance from the outside of one scale to the inside of the other. Another way of saying this is the thickness of the knife minus the thickness of one handle scale. You don't need to be exact at this point.

Then mark the angle of the tang of the knife while it is open, and cut a thin slit at that point.. I wouldn't advise drilling ans many holes as I did, as it causes some play in the lock.

Insert the metal strip into the slit and bend it 90 degrees down so it is flush with the handle scales.  Next assemble the knife with blade and washer. Now move the lock as far as it will go towards the scale that doesn't have the slit. It should now lie flush with the far scale. then bend the outside 90 degrees.

Step 6: Backspacer and Final Assembly

Now we need to firm up the knife. the handle scales will need to be joined. I did this by cutting a thin slice of wood (about the same thickness as a handle scale) and sanding it until it was the same thickness as the distance between both handle scales. 

Make sure that it is as flat as possible, and that it is not to wide, because the the lock won't work.  Don't worry to much the lock can be re bent later, but it won't look as nice.

Then glue and nail all three pieces together. I recommend drilling small holes before putting the nails in.  It is also important to ensure that the nail on the bottom of the knife goes through the locking clip securing it to the handle scale. I don't think this affects performance but it will stop an annoying rattling sound.

Next cut and file the nails so they lay flush with the handle scales.

Next we need to sharpen the blade.

Step 7: Sharpening and Final Touches

This is were the piece of metal becomes a useful tool. I used the grinder to set the grind, and then a series of sharpening stones to sharpen the blade. I did about 20 degrees. I am by no means an expert on sharpening, but I got the knife reasonably sharp. Those of you with experience should be able to achieve better results. 

Start by grinding about half a centimeter of the blade to about 30 degrees, then repeat on the other side.  Next move on to a rough stone, sharpening curved blades like this can be tricky so I went in small circles moving back and forth, rather than the traditional arc. Once the bevel is even, when it catches the light it should be one even reflecting surface, not many different angled facets.  Move on to a higher grit stone, On the high quality stones I used the traditional  arcs rather than small circles(back and forth). Move your way up until you run out of stones, by now the knife should be pretty sharp.

Here are a few videos detailing how to sharpen knives.

By now the wood of the handle scales is probably pretty dirty, I sanded everything and applied a dark stain. Follow the instructions on the can for applying stain. 

And now you have you're vary own pocket knife, which probably only cost a few bucks. I was really surprised at how sharp a disk brake was able to get, I'm not sure yet how long it will hold that edge.  It slices paper and shaves wood pretty well. Hope you had fun building it, and please use it responsibly.

Stay tuned as I plan on making a high quality knife and uploading instructions here in the next couple months.

As always any tips or tricks you have concerning the instructable are greatly appreciated. So are ratings and votes:)

Thanks  for reading

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